Things weren’t so hot for the American economy and a lot else in 2010, but for the health of the American people, it was a pretty good year.

Life expectancy improved, mortality rates fell for all five leading causes of death, and the homicide rate was as low as it has been in almost 50 years, according to data released Wednesday.

The gap in life expectancy between whites and blacks narrowed slightly, although the difference between men and women remained unchanged, at 4.9 years. Hispanic men and women continued to have the longest life expectancy, a finding that has puzzled demographers in recent years but that now appears to be unquestionable.

“We sort of expected those trends would continue, but what grabbed us here was the drop in homicide,” said Robert N. Anderson, chief of mortality statistics at the National Center for Health Statistics.

Homicide climbed into the top 15 causes of U.S. deaths in 1965. It placed tenth for three years in the early 1990s. In recent years, it has been hovering at 13 or 14. In 2010, it fell to 16.

The steep drop in homicide in the 1990s — the District’s rate is now less than a third of what it was in 1991 — is usually attributed to crack cocaine’s waning popularity. Experts are less able to explain the decline since 2008, a period that tracks the economic downturn.

“There’s not enough knowledge out there for us to have an explanation that we can bank on. We’re left with speculation,” said Alfred Blumstein, a criminologist at Heinz College of Carnegie Mellon University in Pittsburgh.

A wide array of theories has been offered about factors that might be contributing to the decline, he said, ranging from better policing to the possibility that a lowered rate of lead poisoning in city children has led to reduced antisocial behavior among young adults.

“I think we can also rule out the ‘business cycle’ as an explanation,” said Philip J. Cook, a professor of economics and public policy at Duke University.

Cook has analyzed the 13 business cycles since 1933 and found that “recessions have little or no effect on the homicide rate. . . . At this point, I think we need to dig into the details of the homicide patterns” to come up with credible reasons for the recent trend, he said.

The new data show that for females in 2010, life expectancy was 83.8 years for Hispanics, 81.1 years for non-Hispanic whites and 77.7 years for non-Hispanic blacks. For males, life expectancy was 78.8 years for Hispanics, 76.4 years for non-Hispanic whites and 71.4 for non-Hispanic blacks. Statistics for 2011 will not be available until next year.

The list of the top 15 causes of deaths also saw a new arrival in 2010 — “pneumonitis due to solids and liquids,” or lung damage from the inhalation of food or water. That’s a problem of demented or bed-confined people, as well as those with certain neuromuscular ailments such as Lou Gehrig’s disease. Three-fourths of people dying from that cause were 75 years or older.

There are three diseases in the top 15 list that are associated strongly with the aging population — Alzheimer’s disease (No. 6), Parkinson’s disease (No. 14) and pneumonitis (No. 15). Stroke (No. 4) is also much more common in elderly people.

The five leading causes of death did not change order in 2010. They were heart disease, cancer, chronic lung disease, stroke and accidents. Accidents were leading cause of death for Americans ages 1 to 44.

In regards to certain diseases, the statistics chart huge improvements in medical care and American health. The rate of death from heart disease in 2010 was less than one-third the rate in 1958, the high-water mark of cardiovascular mortality. About half that gain is from better medicine and half from an improved “risk profile” — less smoking, lower cholesterol — in the United States population. The cancer mortality rate has been falling since 1993 and is now 20 percent lower than it was that year. The greater life expectancy of Hispanics is known as the “Hispanic paradox” because Hispanics as a group have less income and education than whites, and those two variables are the strongest predictors of longevity. Possible explanations are less smoking in Hispanics and that people who emigrate tend to be healthier than people who stay in their native countries. But that can’t be the whole story, because the “paradox” is found with United States-born Hispanics, too.

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